• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 15
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 46
  • 34
  • 8
  • 7
  • 7
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

The IRMA III control and communication system

Schofield, Ian Sean, University of Lethbridge. Faculty of Arts and Science January 2005 (has links)
The IRMA III infrared radiometer is a passive atmospheric water vapor detector designed for use with interferometric submillimeter arrays as a method of phase correction. The IRMA III instrument employs a distributed, multi-tasking software control system permitting precise fine-grained control at remote locations over a low-bandwidth network connection. IRMA's software is divided among three processors tasked with performing three primary functions: command interpretation, data collection and motor control of IRMA's Alt-Az mount. IRMA's hardware control and communication functionality is based on compact, low cost, energy efficient Rabbit 2000 microcontroller modules, selected to meet IRMA's limited space and power requirements. IRMA accepts scripts defined in a custom, high level control language as its method of control, which the operator can write or dynamically generated by a separate GUI front-end program. / xi, 193 leaves : ill. ; 28 cm.
32

IRMA calibrations and data analysis for telescope site selection

Querel, Richard Robert, University of Lethbridge. Faculty of Arts and Science January 2007 (has links)
Our group has developed a 20 μm passive atmospheric water vapour monitor. The Infrared Radiometer for Millimetre Astronomy (IRMA) has been commissioned and deployed for site testing for the Thirty Meter Telescope (TMT) and the Giant Magellan Telescope (GMT). Measuring precipitable water vapour (PWV) requires both a sophisticated atmospheric model (BTRAM) and an instrument (IRMA). Atmospheric models depend on atmospheric profiles. Most profiles are generic in nature, representing only a latitude in some cases. Site-specific atmospheric profiles are required to accurately simulate the atmosphere above any location on Earth. These profiles can be created from publicly available archives of radiosonde data, that offer nearly global coverage. Having created a site-specific profile and model, it is necessary to determine the PWV sensitivity to the input parameter uncertainties used in the model. The instrument must also be properly calibrated. In this thesis, I describe the radiometric calibration of the IRMA instrument, and the creation and analysis of site-specific atmospheric models for use with the IRMA instrument in its capacity as an atmospheric water vapour monitor for site testing. / xii, 135 leaves : ill. ; 28 cm. --
33

Optimisation of the instrumental performance of IRMA

Dahl, Regan Eugene, University of Lethbridge. Faculty of Arts and Science January 2008 (has links)
The Infrared Radiometer for Millimetre Astronomy (IRMA) is a passive atmospheric water vapour monitor developed at the University of Lethbridge. It is a compact, robust, and autonomous instrument, which is capable of being operated remotely. The latest model is based on a PC/104 running an AMD 133 MHz SC520 processor, which allows for more flexible control of the unit. The modifications and upgrades to the software required for the transition to this new platform are discussed in this thesis. In addition to software optimisation, a new calibration method has been developed as the unit has become better understood. This method has been verified through test campaigns carried out in Lethbridge and Chile. The results of these tests are included in this thesis. / xii, 141 leaves : ill. (some col.) ; 28 cm. --
34

Correlation of rain dropsize distribution with rain rate derived from disdrometers and rain gauge networks in Southern Africa.

Alonge, Akintunde Ayodeji. January 2011 (has links)
Natural phenomena such as rainfall are responsible for communication service disruption, leading to severe outages and bandwidth inefficiency in both terrestrial and satellite systems, especially above 10 GHz. Rainfall attenuation is a source of concern to radio engineers in link budgeting and is primarily related to the rainfall mechanism of absorption and scattering of millimetric signal energy. Therefore, the study of rainfall microstructure can serve as a veritable means of optimizing network parameters for the design and deployment of millimetric and microwave links. Rainfall rate and rainfall drop-size are two microstructural parameters essential for the appropriate estimation of local rainfall attenuation. There are several existing analytical and empirical models for the prediction of rainfall attenuation and their performances largely depend on regional and climatic characteristics of interest. In this study, the thrust is to establish the most appropriate models in South African areas for rainfall rate and rainfall drop-size. Statistical analysis is derived from disdrometer measurements sampled at one-minute interval over a period of two years in Durban, a subtropical site in South Africa. The measurements are further categorized according to temporal rainfall regimes: drizzle, widespread, shower and thunderstorm. The analysis is modified to develop statistical and empirical models for rainfall rate using gamma, lognormal, Moupfouma and other ITU-R compliant models for the control site. Additionally, rain drop-size distribution (DSD) parameters are developed from the modified gamma, lognormal, negative exponential and Weibull models. The spherical droplet assumption is used to estimate the scattering parameters for frequencies between 2 GHz and 1000 GHz using the disdrometer diameter ranges. The resulting proposed DSD models are used, alongside the scattering parameters, for the prediction and estimation of rainfall attenuation. Finally, the study employs correlation and regression techniques to extend the results to other locations in South Africa. The cumulative density function analysis of rainfall parameters is applied for the selected locations to obtain their equivalent models for rainfall rate and rainfall DSD required for the estimation of rainfall attenuation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
35

Improving linearity utilising adaptive predistortion for power amplifiers at mm-wave frequencies

Valliarampath, J.T. (Joe) January 2014 (has links)
The large unlicensed 3 GHz overlapping bandwidth that is available worldwide at 60 GHz has resulted in renewed interest in 60 GHz technology. This frequency band has made it attractive for short-range gigabit wireless communication. The power amplifier (PA) directly influences the performance and quality of this entire communication chain, as it is one of the final subsystems in the transmitter. Spectral efficient modulation schemes used at 60 GHz pose challenging requirements for the linearity of the PA. To improve the linearity, several external linearisation techniques currently exist, such as feedback, feedforward, envelope elimination and restoration, linear amplification with non-linear components and predistortion. This thesis is aimed at investigating and characterising the distortion components found in PAs at mm-wave frequencies and evaluating whether an adaptive predistortion (APD) linearisation technique is suitable to reduce these distortion components. After a thorough literature study and mathematical analysis, it was found that the third-order intermodulation distortion (IMD3) components were the most severe distortion components. Predistortion was identified as the most effective linearisation technique in terms of minimising these IMD3 components and was therefore proposed in this research. It does not introduce additional complexity and can easily be integrated with the PA. Furthermore, the approach is stable and has lower power consumption when compared to the aforementioned linearisation techniques. The proposed predistortion technique was developed compositely through this research by making it a function of the PA’s output power that was measured using a power detector. A comparator was used with the detected output power and the reference voltages to control the dynamic bias circuit of the variable gain amplifier. This provided control and flexibility on when to apply the predistortion to the PA and therefore allowing the linearity of the PA to be optimised. Three-stage non-linear and linear PAs were also designed at 60 GHz and implemented to compare the performance of the APD technique and form part of the hypothesis verification process. The 130 nm silicon-germanium (SiGe) bipolar and complementary metal oxide semiconductor (BiCMOS) technology from IBM was used for the simulation of the entire APD and PA design and for the fabrication of the prototype integrated circuits (ICs). This technology has the advantage of integrating the high performance, low power intensive SiGe heterojunction bipolar transistors (HBTs) with the CMOS technology. The SiGe HBTs have a high cut-off frequency ( > 200 GHz), which is ideal for mm-wave PA applications and the CMOS components were integrated in the control logic of the digital circuitry. The simulations and IC layout were accomplished with Cadence Virtuoso. The implemented IC occupies an area of 1.8 mm by 2.0 mm. The non-linear PA achieves a of 11.97 dBm and an of -10 dBm. With the APD technique applied, the linearity of the PA is significantly improved with an of -6 dBm and an optimum IMD3 reduction of 10 dB. Based on the findings and results of the applied APD technique, APD reduced intermodulation distortion (especially the IMD3) and is thus suitable to improve the linearity of PAs at mm-wave frequencies. To the knowledge of this author, no APD technique has been applied for PAs at 60 GHz, therefore the contribution of this research will assist future PA designers to characterise and optimise the reduction of the IMD3 components. This will result in improved linear output power from the PA and the use of complex modulation schemes at 60 GHz. ## Die groot ongelisensieerde oorvleuelde bandwydte van 3 GHz wat wêreldwyd by 60 GHz beskikbaar is, het hernude belangstelling in 60 GHz-tegnologie tot gevolg gehad. Hierdie frekwensieband het dit aantreklik gemaak vir kortafstand-gigabis draadlose kommunikasie. Aangesien die drywingsversterker een van die finale subsisteme in die seintoestel is, het dit ’n direkte invloed op die werkverrigting en kwaliteit van die hele kommunikasieketting. Spektraaldoeltreffende modulasieskemas wat by 60 GHz gebruik word, stel uitdagende vereistes vir die lineariteit van die drywingsversterker. Om die lineariteit te verbeter, is daar tans verskeie eksterne linearisasietegnieke beskikbaar, soos terugvoer, vooruitvoer, omhullende eliminasie en -restorasie, lineêre versterking met nie-lineêre komponente en predistorsie. Hierdie tesis het ten doel om die distorsiekomponente wat by millimetergolffrekwensies in drywingsversterkers gevind word, te ondersoek en te karakteriseer en om te bepaal of ’n aanpassende predistorsielinearisasietegniek geskik is om hierdie distorsiekomponente te verminder. Na ’n deeglike literatuurstudie en wiskundige analise is gevind dat die derde-orde-intermodulasiedistorsiekomponente (IMD3) die ergste distorsiekomponente was. Predistorsie is geïdentifiseer as die mees effektiewe linearisasietegniek om hierdie IMD3-komponente te minimeer en die gebruik daarvan is gevolglik in hierdie navorsing voorgestel. Dit bring nie addisionele kompleksiteit mee nie en kan maklik met die drywingsversterker geïntegreer word. Daarbenewens is die benadering stabiel, met laer kragverbruik in vergelyking met die linearisasietegnieke wat voorheen genoem is. Die voorgestelde predistorsietegniek is in hierdie navorsing ontwikkel deur dit ’n funksie van die drywingsversterker se uitsetkrag te maak, wat gemeet is deur ’n kragdetektor te gebruik. ’n Vergelyker is saam met die gemete uitsetkrag en die verwysingspannings gebruik om die dinamiese voorspanningsbaan van die veranderlike winsversterker te beheer. Dit het toegelaat vir beheer en buigsaamheid in die aanwending van die predistorsie op die drywingsversterker en gevolglik vir die optimering van die lineêriteit van die drywingsversterker. Driefase- nie-lineêre en lineêre drywingsversterkers is ook by 60 GHz ontwerp en geïmplementeer om die werkverrigting van die aanpassende predistorsietegniek te vergelyk en dit vorm deel van die verifikasieproses van die hipotese. Die 130 nm-silikon-germanium (SiGe) bipolêre en metaaloksiedhalfgeleier- (BiCMOS) tegnologie van IBM is gebruik vir die simulasie van die hele aanpassende predistorsietegniek- en drywingsversterkerontwerp en vir die vervaardiging van die prototipe- geïntegreerde stroombane. Hierdie tegnologie het die voordeel dat dit die hoë werkverrigting en lae krag-intensiewe SiGe-heterovoegvlak-bipolêre transistors (HBTs) met die CMOS-tegnologie integreer. Die SiGe-HBTs het ’n hoë afsnyfrekwensie ( > 200 GHz), wat ideaal is vir mm-golfdrywingsversterkeraanwendings en die CMOS-komponente is in die beheer-logika van die digitale stroombaan geïntegreer. Die geïntegreerde stroombaan beslaan ’n area van 1.8 mm by 2.0 mm. Die nie-lineêre drywingsversterker behaal ’n van 11.97 dBm en ’n van -10 dBm. As die APD-tegniek toegepas word, word die lineariteit van die drywingsversterker beduidend verbeter tot ’n van -6 dBm en ’n optimum-IMD3-vermindering van 10 dB. Volgens die bevindings en resultate van die APD-tegniek wat toegepas is, verminder APD intermodulasiedistorsie (veral die IMD3) en is gevolglik geskik om die lineariteit van drywingsversterkers by mm-golffrekwensies te verbeter. Na die wete van hierdie skrywer is daar nie voorheen enige APD tegniek toegepas vir drywingsversterkers by 60 GHz nie, gevolglik sal die bydrae van hierdie navorsing toekomstige drywingsversterkerontwerpers help om die vermindering van die IMD3-komponente te karakteriseer en optimeer. Dit sal verbeterde lineêre uitsetkrag van die drywingsversterker tot gevolg hê, asook meer komplekse modulasieskemas by 60 GHz toelaat. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Electrical, Electronic and Computer Engineering / PhD / unrestricted
36

Nouvelles antennes pourr radar millimétriques / New antenna for millimetre wave radar

Bin Zawawi, Muhammad Nazrol 24 April 2015 (has links)
L’objectif de cette thèse est de concevoir un réseau réflecteur à dépointage électronique à 20 GHz pour des applications de communication avec des drones (Unmanned Aerial System). Le principe de fonctionnement des réseaux réflecteurs est similaire à celui d’une antenne parabolique. La principale différence concerne la forme du réflecteur. En effet les panneaux des réseaux réflecteurs sont plans contrairement à la parabole. Le panneau réflecteur se compose de cellules élémentaires qui sont utilisées pour contrôler la phase réfléchie de l’onde d’incidente. Le contrôle de la phase au niveau de la cellule élémentaire nous permet de focaliser le diagramme de rayonnement dans la direction souhaitée. Dans cette thèse, la solution retenue est l’utilisation de diodes PIN. Cette dernière a fait l’objet de nombreuses études que ce soit au niveau laboratoire mais également industriel et possède des atouts intéressant en terme de performance et de coût. L'étude montre que d'avoir un niveau de correction élevée ne garantit pas la meilleure performance parce qu'il faut aussi considérer les pertes dans l'élément actif lui-même (dans notre cas, il s’agit des pertes dans les diodes PIN). Dans l’avenir, il serait nécessaire de modifier la position de la diode afin de rendre la fabrication plus aisée. Dans ce cas il faudra retravailler sur les lignes de polarisation et aussi les géométries du stub et des vias. Il sera peut-être nécessaire de déplacer la diode à l'extérieur du substrat en face l'arrière de la cellule par exemple. Quand les réseaux réflecteurs seront fabriqués, ils pourront être directement testés avec le contrôleur de diode fabriqué. / The objective of this project is to design and fabricate a reconfigurable reflectarray with beam scanning capability at 20 GHz for unmanned aerial system (UAS) communication link. Reflectarray is a type of antenna that shares similar functionality to parabolic reflector antenna. The main difference is the physical and geometry appearance of the antenna where reflectarray has flat reflecting panel instead of parabolic reflector. The reflecting panel consists of elementary cell, which is used to control the reflected phase of the incident wave. By controlling the reflected phase on each elementary cell, the radiation pattern of the antenna can be focused to any desired direction. PIN diode technology is chosen as the preferred solution in the context of this project because it is already proven working in the industry and research fields. In house reflectarray simulator has been developed from the simulation, having high correction order will not necessarily improve the performance because the loss inside in active element must also be considered. In the short-term period, the modification on the elementary cell diode polarization line will enable the reflectarray to be fabricated and measured because the current design cannot be fabricated by the manufacturer contrary to their first statement due to position of the diode in the middle of substrates. The modification requires the p-i-n diode to be moved at the backside of the elementary cell and some geometry adjustments are needed for the phase delay line and the via. Once the reflectarray is fabricated, it can be tested directly with the diode controller that is already validated and shown to be working well.
37

Improving linearity utilising adaptive predistortion for power amplifiers at mm-wave frequencies

Valliarampath, J.T. (Joe) 29 July 2014 (has links)
The large unlicensed 3 GHz overlapping bandwidth that is available worldwide at 60 GHz has resulted in renewed interest in 60 GHz technology. This frequency band has made it attractive for short-range gigabit wireless communication. The power amplifier (PA) directly influences the performance and quality of this entire communication chain, as it is one of the final subsystems in the transmitter. Spectral efficient modulation schemes used at 60 GHz pose challenging requirements for the linearity of the PA. To improve the linearity, several external linearisation techniques currently exist, such as feedback, feedforward, envelope elimination and restoration, linear amplification with non-linear components and predistortion. This thesis is aimed at investigating and characterising the distortion components found in PAs at mm-wave frequencies and evaluating whether an adaptive predistortion (APD) linearisation technique is suitable to reduce these distortion components. After a thorough literature study and mathematical analysis, it was found that the third-order intermodulation distortion (IMD3) components were the most severe distortion components. Predistortion was identified as the most effective linearisation technique in terms of minimising these IMD3 components and was therefore proposed in this research. It does not introduce additional complexity and can easily be integrated with the PA. Furthermore, the approach is stable and has lower power consumption when compared to the aforementioned linearisation techniques. The proposed predistortion technique was developed compositely through this research by making it a function of the PA’s output power that was measured using a power detector. A comparator was used with the detected output power and the reference voltages to control the dynamic bias circuit of the variable gain amplifier. This provided control and flexibility on when to apply the predistortion to the PA and therefore allowing the linearity of the PA to be optimised. Three-stage non-linear and linear PAs were also designed at 60 GHz and implemented to compare the performance of the APD technique and form part of the hypothesis verification process. The 130 nm silicon-germanium (SiGe) bipolar and complementary metal oxide semiconductor (BiCMOS) technology from IBM was used for the simulation of the entire APD and PA design and for the fabrication of the prototype integrated circuits (ICs). This technology has the advantage of integrating the high performance, low power intensive SiGe heterojunction bipolar transistors (HBTs) with the CMOS technology. The SiGe HBTs have a high cut-off frequency (fT > 200 GHz), which is ideal for mm-wave PA applications and the CMOS components were integrated in the control logic of the digital circuitry. The simulations and IC layout were accomplished with Cadence Virtuoso. The implemented IC occupies an area of 1.8 mm by 2.0 mm. The non-linear PA achieves a Psat of 11.97 dBm and an IP1dB of -10 dBm. With the APD technique applied, the linearity of the PA is significantly improved with an IP1dB of -6 dBm and an optimum IMD3 reduction of 10 dB. Based on the findings and results of the applied APD technique, APD reduced intermodulation distortion (especially the IMD3) and is thus suitable to improve the linearity of PAs at mm-wave frequencies. To the knowledge of this author, no APD technique has been applied for PAs at 60 GHz, therefore the contribution of this research will assist future PA designers to characterise and optimise the reduction of the IMD3 components. This will result in improved linear output power from the PA and the use of complex modulation schemes at 60 GHz. / Thesis (PhD)--University of Pretoria, 2014. / Electrical, Electronic and Computer Engineering / PhD
38

Aspects of small airborne passive millimetre-wave imaging systems

Smith, David Michael Patrick 03 1900 (has links)
Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Passive millimetre-wave (PMMW) imaging is a technique that uses radiometers to detect thermal radiation emitted and reflected by metallic and non-metallic objects. While visual and infra-red emissions are attenuated by atmospheric constituents, PMMW emissions are transmitted, resulting in consistent contrast between different objects from day to night in clear weather and in low-visibility conditions to form images for a range of security and inclement weather applications. The use of a PMMW imaging system on a small unmanned aerial vehicle (UAV) offers extremely attractive possibilities for applications such as airborne surveillance for search and rescue operations, which are often hindered by inclement weather making visibility poor and endangering the rescuers as the search vehicle flies through the bad weather zone. The UAV would fly above the bad weather zone, with the PMMW imaging system detecting the thermal radiation emitted and reflected by objects in the MMW spectrum through the inclement weather. The 35GHz propagation window is chosen for the greater transmission through atmospheric constituents. The design of the PMMW imaging system is severely limited by the size of the UAV, particularly in the inability to incorporate any form of optical or mechanical scanning antenna. A possible solution is a long, thin antenna array fitted under the wings of the UAV. Such an antenna has a narrow, high gain, frequency-scanned beam along the plane perpendicular to the flight path, but a very broad beam along the plane of the flight path blurs the image, making it difficult to accurately determine the position of an object or to differentiate between objects situated along the plane of the flight path. This dissertation proposes a technique of image reconstruction based on the Kalman filter, a recursive filter that uses feedback control to estimate the state of a partially observed non-stationary stochastic process, to reconstruct an accurate image of the target area from such a detected signal. It is shown that given a simulated target area, populated with an arbitrary number of objects, the Kalman filter is able to successfully reconstruct the image using the measured antenna pattern to model the scanning process and reverse the blurring effect / AFRIKAANSE OPSOMMING: Passiewe millimetergolf (PMMG) beeldvorming is ’n tegniek wat van radiometers gebruik maak om termiese straling waar te neem vanaf beide metaal en nie-metaal voorwerpe. Waar optiese en infra-rooi straling attenueer word deur atmosferiese bestanddele, plant PMMG strale ongehinderd voort. Dit lei tot konstante kontras tussen verskillende voorwerpe in daglig of snags, mooi of bewolkte weer, en in ander lae-sigbaarheid toestande om beelde te vorm vir ’n wye reeks sekuriteits- of weertoepassings. Die gebruik van PMMG beeldvorming op ’n klein onbemande lugtuig (OLT) bied aantreklike moontlikhede vir toepassings in observasie en reddingsoperasies, wat dikwels verhinder word deur bewolke weer wat reddingswerkers in gevaar stel as hul moet vlieg in toestande van lae sigbaarheid. Die OLT kan bokant die onweer vlieg, met die PMMG beeldvormer wat termiese straling in die millimetergolf spektrum vanaf voorwerpe kan waarneem in swaks weerstoestande. Vir verbeterde golfvoortplanting deur atmosferiese bestanddele, word die 35GHz band gekies. Die ontwerp van die PMMG stelsel word geweldig beperk deur die grootte van die OLT, spesifiek deur die tuig se onvermoë om ’n antenne te huisves wat opties of meganies kan skandeer. ’n Moontlike oplossing is om gebruik te maak van ’n lang, dun antenne samestelling wat onder die OLT se vlerke geplaas word. So ’n antenne het ’n nou, hoë-aanwins bundel wat met frekwensie skandeer langs ’n vlak loodreg tot die vlugtrajek. So ’n antenne het egter ’n baie wye bundel langs die vlugtrajek, wat beeldkwaliteit verlaag en dit moeilik maak om die posisie van ’n voorwerp langs die vlugtrajek te bepaal, of om tussen veelvuldige voorwerpe te onderskei. Hierdie proefskrif bied ’n tegniek van beeldherwinning gebaseer op die Kalman filter, ’n rekursiewe filter wat terugvoerbeheer gebruik om die toestand van ’n nie-stasionêre stochastiese proses af te skat wat slegs gedeeltelik waargeneem is, om soedoende ’n akkurate beeld van die teikenarea te herkonstrueer vanuit ’n verwronge beeld. Dit word getoon dat, gegewe ’n gesimuleerde teikenomgewing met ’n arbitrêre hoeveelheid voorwerpe, die Kalman filter suksesvol ’n beeld kan herkonstrueer deur gebruik te maak van die antenne se gemete stralingspatroon om die skanderingsproses na te boots, om sodoende die beeldkwaliteit te verhoog
39

Structure and optimisation of liquid crystal based phase shifter for millimetre-wave applications

Li, Jinfeng January 2019 (has links)
The delivery of tunable millimetre-wave components at 60GHz is of research and development interests with the advent of 5G era. Among applications such as high-data-rate wireless communications, high-precision automotive radars and hand-gesture sensing, variable phase shifters are vital components for antenna arrays to steer an electromagnetic beam without mechanical movement. However, present microwave technology has limited scope in meeting more and more stringent requirements in wavefront phase control and device performance for those cutting-edge applications in the millimetre-wavelength range. Although some existing microwave switchable techniques (such as RF MEMS and solid-state p-i-n diodes) can offer ultra-fast speed for phase modulation, their binary beam-steering nature is resolution-limited and thereby degrades the beam-scanning performance. In response to this, continuously-tunable phase shifting can be realised by using tunable dielectric materials such as ferroelectric BST and liquid crystals (LCs). BST thin films can offer relatively fast switching and modest tunability. However, the increased dielectric loss beyond 10GHz impedes their implementation for higher frequency applications. By comparison, liquid crystals (LCs) have drawn attention in recent years because of their continuous tunability as well as low losses especially at millimetre-wavebands. The principle of shifting the phase continuously is based on the shape anisotropy of LC molecules for variable polarizabilities and hence tunable dielectric constants, which allows wave speed to be controlled with ease by a low-frequency field of only up to 10V. However, LC-based tunable delay lines are not well established in the frequency regime of 60GHz-90GHz because of the limited status of LC microwave technology in which most of the LC based devices have been designed for below 40GHz. It is the aim of this PhD research to bridge the gap and address future societal needs based on our group's focus and experience in developing cutting-edge LC-based agile microwave components. In this work, a liquid crystal (LC) based 0-180˚continuously-variable phase shifter is developed with insertion loss less than -4.4dB and return loss below -15dB across a wide spectrum from 54GHz to 67GHz. The device is driven by a 0-10V AC bias and structured in a novel enclosed coplanar waveguide (ECPW) including an enclosed ground plate in the design, which significantly reduces the instability due to floating effects of the transmission line. This structure screens out interference and stray modes, allowing resonance-free quasi-TEM wave propagation up to 90GHz. The tunable ECPW is optimised by competing spatial volume distribution of the millimetre-wave signal occupying lossy tunable dielectrics versus low-loss but non-tunable dielectrics and minimising the total of dielectric volumetric loss and metal surface loss for a fixed phase-tuning range. A variety of influences affecting the actual device performance are studied, experimented and optimised. Fabricated prototypes exhibit wideband low-loss performance and 0-π continuous tuning with low power consumptions and high linearity compared with the state-of-the-arts. Potentially, the ECPW-fed phased antenna array will be incorporated with advanced beam-forming algorithms to develop compact beam-steering systems of improved performances and targeted for ultra-high-data-rate wireless communications, inter-satellite communications, current road safety improvement, futuristic autonomous driving, and other smart devices such as the hand-gesture recognition.
40

Conception et réalisation de fonctions millimétriques en technologie BiCMOS 55nm / Design and realization of millimeter wave circuits in advanced BiCMOS 55nm technology

Serhan, Ayssar 28 September 2015 (has links)
Au cours des dernières années, la faisabilité des émetteurs-récepteurs millimétriques entièrement intégrés a été largement démontrée en technologies silicium CMOS et BiCMOS. Deux axes sont actuellement très porteurs dans ce domaine : (1) l’amélioration des performances à travers des boucles d’asservissement intégrées (ALC : Automatique Level Control), (2) le développement de solutions de caractérisation sur silicium des composants millimétriques (BIT : Built In Test). L’objectif principal de cette thèse est de développer les blocsde base (détecteurs de puissance et baluns) pour répondre aux besoins actuels des applications ALC et BIT. Les circuits réalisés combinent l’avantage de composants actifs de la technologie BiCMOS 55 nm, de STMicroelectronics, avec l’avantage des structures passives à ondes lentes développées à l’IMEP-LAHC. Ce travail permet un développement plus rapide et robuste pour la future génération de systèmes millimétriques. / In the past few years, the feasibility of high performance millimeter-wave(mmWave) fully-integrated transceivers has been widely demonstrated in both CMOS andBiCMOS silicon technologies. Nowadays, automatic level control (ALC) solutions and in-situtesting (BIT: Built in Testing) and characterization of mmWave components, constitute themajor research interest in mmWave domain. This work focus on the development of the mainbuilding blocks (power detectors and baluns) that meet the requirement of the today’smmWave ALC and BIT applications. The developed prototypes take advantage of the highperformances transistors offered by the BiCMOS 55 nm technology, from STMicroelectronics, aswell as the high performances of the slow-wave based passive components developed by theIMEP-LAHC laboratory. Several prototypes were developed as a proof of concept for thedesignated applications. This work helps future generation millimeter-wave systems to havefaster development and better robustness.

Page generated in 0.0792 seconds